Crankshaft Main Bearings Service
- Remove main bearing caps. See Fig 1 . Check main bearing clearances using Plastigage method. If clearance is excessive, install new bearings. If clearance is still excessive, regrind crankshaft and install undersize bearings.
- Replacement bearings are available in standard, .010" (.25 mm) undersize and also .020" (.50 mm) undersize. With crankshaft removed from engine, measure diameter of crankshaft journals and crankpins at front, rear and in 2 directions to check for wear and taper.
- If taper exceeds .002" (.05 mm), regrind or replace crankshaft. Check crankshaft runout, by placing "V" blocks under crankshaft at No. 1 and No. 5 journals. Position dial indicator point on No. 3 journal. Slowly turn crankshaft, while noting runout. If runout exceeds .004" (.1 mm), replace or correct crankshaft.
- Lubricate engine bearings. Install main bearing caps in original position with arrow pointing toward front of engine. Lubricate main bearing cap bolts. Tighten main caps to specification in reverse order of removal. Ensure crankshaft turns freely.